The present disclosure relates to a microphone and a sound pickup method.
Sound localization techniques include, for example, an out-of-head localization technique, which localizes sound images outside the head of a listener by using headphones. The out-of-head localization technique localizes sound images outside the head by canceling characteristics from the headphones to the ears and giving four characteristics (spatial acoustic transfer characteristics) from stereo speakers to the ears.
In out-of-head localization reproduction, measurement signals (impulse sounds etc.) that are output from 2-channel (which is referred to hereinafter as “ch”) speakers are recorded by microphones (which can be also called “mike”) placed on the listener's ears. Then, a processing unit generates a filter based on sound pickup signals obtained by impulse responses. The generated filter is convolved to 2-ch audio signals, thereby implementing out-of-head localization reproduction.
Further, in order to generate a filter for cancelling characteristics from the headphones to the ears, characteristics from the headphones to the ears or eardrums (which are also referred to as an “ear-canal transfer function ECTF” or “ear-canal transfer characteristics”) are measured by using microphones placed in the listener's ears.
Japanese Unexamined Patent Application Publication No. 2015-126267 discloses earphones/microphones that can be worn on user's ears. Each of the earphones/microphones disclosed in Japanese Unexamined Patent Application Publication No. 2015-126267 includes a housing, a speaker, an ear piece, and a microphone. The housing includes a housing part for storing the speaker and a sound tube part in which the microphone is disposed. The sound tube part of the housing is attached to the ear piece.
In order to perform an out-of-head localization process, it is preferable to measure both of spatial acoustic transfer characteristics and ear-canal transfer characteristics for each individual person. In Japanese Unexamined Patent Application Publication No. 2015-126267, a measurement unit for measuring a head-related transfer function (HRTF), which is spatial acoustic transfer characteristics, and a measurement unit for measuring ear-canal transfer characteristics are separately prepared. That is, two ear pieces having the same shape are prepared. Further, microphones are disposed in their sound tube parts so that the positions of the microphones relative to the ear pieces coincide with each other.
In Japanese Unexamined Patent Application Publication No. 2015-126267, the spatial acoustic transfer characteristics and the ear-canal transfer characteristics are measured by different microphones. Therefore, there is a possibility that the measured characteristics could vary due to the individual differences of the microphones. It is desired that the microphones be placed as close to the ear drums as possible.